Gaia, thanks for your reply. I have taken Jupiter to Puppy Obedience, Obedience I, and Obedience II, at all4paws training, which is a reputable place here in Tempe, and I train him every day with his kibble. He is excellent in class and in the kitchen, but unfortunately, I have not done a good job of extending that outside the house, where he only listens to me if there's nothing else going on. He is an independent-minded (stubborn) dog and is very food-oriented.
Lately, I have been making an extra effort to keep drilling recall, and have started interspersing "come" during walks and randomly throughout the day, but the dog park is a whole other level of stimulation. Once in a while, he's broken off pursuit at my call, but other times, he has ignored me.